The present invention relates to an improved apparatus for finishing concrete surfaces, particularly in applications involving large surface areas.
If concrete is allowed to cure normally without interference, random accumulations of sand, rock or gravel, the principal components of concrete, will be visible on the top surface. For appearance reasons, it is therefore generally considered desirable to subject the poured concrete to a process commonly known as "floating" which ultimately results in the submersion of the solid particulate matter within the mixture, allowing the smoother liquid cement to appear on the surface. A long handled, bladed device, usually made of magnesium or aluminum and referred to as a "float" will accomplish this purpose when drawn across the wet surface. The cement can then be finished to the desired texture and consistency. In concrete construction of a relatively small scale, the finishing process may be accomplished by hand, using well known troweling methods and tools.
In modern construction practice, however, it is commonplace to encounter situations where concrete is poured over much larger areas. Parking garage surfaces, factory or warehouse floors and even slab foundations in residential building construction all involve the placement of large amounts of concrete. Although perfectly smooth concrete surfaces, such as may be found desirable in sidewalks, patios, etc., may not be required in applications such as those described, a consistent pattern in the surface, completely uniform in spacing and appearance is still highly desirable for aesthetic reasons. Obviously hand troweling and similar concrete finishing methods customarily employed in construction projects of smaller size are entirely impractical in tasks of such magnitude.
At the present time there is generally recognized in the prior art only one basic method of finishing large areas of concrete. Familiar push brooms such as are commonly used in sweeping floors are pulled across the drying concrete surface, leaving a pattern formed by the bristles as they pass across. Such brooms will ordinarily be found to possess threaded apertures into which a handle with perhaps one or more extensions may be fitted. This construction permits the broom to be drug across a concrete surface of area comparable to the length of the handle. For practical purposes, however, such a device becomes increasingly unwieldly as the length of the handle is increased, it being the general experience that a workman is unable to guide the broom and achieve consistent finishing at distances much greater than eighteen feet. If a concrete surface that is to be finished has dimensions greater than eighteen feet, therefore, it is necessary that the workmen actually step upon the surface itself in order to reach all areas. The concrete must be in a relatively advanced state of curing to support the worker's weight as he traverses its surface, and accordingly it is often necessary to have a greater number of persons employed in the finishing process than would be the case on smaller jobs. Since many areas of the concrete surface can not feasibly be reached until curing has progressed to a stage allowing a person to walk on it, in order to finish all areas before the concrete has completely cured or "set up", it is mandatory that an adequate number of workers with finishing brooms be utilized. As the brooms are pulled back across the concrete, the worker's footprints are to some extent eradicated by the textured impressions made by the broom itself, but troweling machines are usually required to completely remove such marks. At the same time some workers are pulling finishing brooms across the concrete surface, another person is required to perform edging work, necessitated by inherent physical limitations of the floating devices. At the edge of the concrete surface a gap or a dip may exist, or rocks or other solid matter may be lying on the surface simply because the workman operating the float may not have been able to manipulate the device along the edge due to spatial constraints. Such areas have to be floated and finished by hand, and since often access to many of these areas can not be permitted until the concrete has already cured somewhat, it is usually required that a worker be specifically assigned to perform the edging work while other workers are finishing the concrete with brooms.
As is well known to those knowledgeable in the industry, existing methods for finishing large concrete surfaces possess many disadvantages, not the least of which is the risk that the concrete will completely "set up" or dry before the entire surface can be finished. The only way to insure that all areas of a large concrete floor can be finished in time, recognizing that the concrete must first be cured to a degree allowing a construction worker to step upon the surface itself, is to employ a sufficiently large number of workers, many more than what would be the case if the finishing work could be commenced sooner in the curing process. With a larger number of different workers and a corresponding number of brooms, it is virtually certain that the finished surface will feature varying degrees of consistency and appearance. Even the work performed by one individual will demonstrate marked variations as he or she progresses, as it is extremely difficult for a worker to draw a broom across one section of concrete surface and then repeat the motion on an adjacent section with any degree of uniformity. As there is no guiding mechanism on the device, it is seldom possible to keep the impressions left by the broom as it passes over the concrete in alignment with those made previously.